Influence of the Oxidation Temperature and Atmosphere on the Reliability of Thick Gate Oxides on the 4H-SiC C(000-1) Face

Abstract:

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The reliability of thermal oxides grown on n-type 4H-SiC C(000-1) face wafer has been
investigated. In order to examine the influence of different oxidation atmospheres and temperatures
on the reliability, metal-oxide-semiconductor capacitors were manufactured and the different oxides
were characterized by C-V measurements and constant-current-stress. The N2O-oxides show the
smallest flat band voltage shift compared to the ideal C-V curve and so the lowest number of effective
oxide charges. They reveal also the lowest density of interface states in comparison to the other oxides
grown on the C(000-1) face, but it is still higher than the best oxides on the Si(000-1) face. Higher
oxidation temperatures result in smaller flat band voltage shifts and lower interface state densities.
Time to breakdown measurements show that the charge-to-breakdown value of 63% cumulative
failure for the N2O-oxide on the C(000-1) face is more than one order of magnitude higher than the
highest values measured on the Si(000-1) face. Therefore it can be concluded that a smaller density of
interface states results in a higher reliability of the oxide.